Assessing regional drought impacts on vegetation and evapotranspiration: a case study in Guanacaste, Costa Rica

Abstract

This research investigates ecological responses to drought by developing a conceptual framework of vegetation response and investigating how multiple measures of drought can improve regional drought monitoring. We apply this approach to a case study of a recent drought in Guanacaste, Costa Rica. First, we assess drought severity with the Standard Precipitation Index (SPI) based on a 64‐yr precipitation record derived from a combination of Global Precipitation Climatology Center data and satellite observations from Tropical Rainfall Measuring Mission and Global Precipitation Measurement. Then, we examine spatial patterns of precipitation, vegetation greenness, evapotranspiration (ET), potential evapotranspiration (PET), and evaporative stress index (ESI) during the drought years of 2013, 2014, and 2015 relative to a baseline period (2002–2012). We compute wet season (May–October) anomalies for precipitation at 0.25° spatial resolution, normalized difference vegetation index (NDVI) at 30‐m spatial resolution, and ET, PET and ESI derived with the Priestley‐Taylor Jet Propulsion Laboratory (PT‐JPL) model at 1‐km spatial resolution. We assess patterns of landscape response across years and land cover types including three kinds of forest (deciduous, old growth, and secondary), grassland, and cropland. Results show that rainfall in Guanacaste reached an all‐time low in 2015 over a 64‐yr record (wet season SPI = −3.46), resulting in NDVI declines. However, ET and ESI did not show significant anomalies relative to a baseline, drought‐free period. Forests in the region exhibited lower water stress compared to grasslands and had smaller declines, and even some increases, in NDVI and ET during the drought period. This work highlights the value of using multiple measures to assess ecosystem responses to drought. It also suggests that agricultural land management has an opportunity to integrate these findings by emulating some of the characteristics of drought‐resilient ecosystems in managed systems.

A catastrophic tropical drought kills hydraulically vulnerable tree species

“…Both sites experience a strong 5–6 month dry season that usually spans from late November to mid‐May. The strong ENSO of 2015 coincided with the lowest reported annual rainfall at Santa Rosa (626 mm) in the existing 35 year record from local, manual gauges (Figure S1) and a 64 year record from global datasets (Cooley et al, 2019). The lowest annual rainfall on record for Palo Verde occurred during 2014 (953 mm).…”

“…During 2015, a severe El Niño Southern Oscillation (ENSO) was associated with a substantial decrease in precipitation and an increase in daily temperature in the tropics (Burton, Rifai, & Malhi, 2018; Cooley et al, 2019). This abnormally strong drought caused major damage to forests in northwestern Costa Rica and in doing so provided the opportunity to investigate the functional characteristics associated with species drought vulnerability under an optimal design, i.e., during an extreme natural event that resulted in high tree mortality.…”

Habitat size thresholds for predators: Why damselflies only occur in large bromeliads

“…Unfortunately, climate change models predict that Central America will lead the world in terms of reduced and more variable precipitation (Giorgi, 2006; Rauscher, Giorgi, Diffenbaugh, & Seth, 2008), with premontane areas of Costa Rica estimated to lose up to 40% of their annual precipitation (Karmalkar, Bradley, & Diaz, 2008). In Guanacaste, variation in precipitation has more than doubled since the year 2000, as compared to the preceding half‐century, including the most severe drought on record in 2015 (Cooley et al, 2019). During the 2015 drought, the most affected area of Guanacaste was the northeast (Cooley et al, 2019), coinciding with the distribution of M. modesta in this province (Amundrud et al, 2018; Hedstrom & Sahlen, 2001).…”

“…In Guanacaste, variation in precipitation has more than doubled since the year 2000, as compared to the preceding half‐century, including the most severe drought on record in 2015 (Cooley et al, 2019). During the 2015 drought, the most affected area of Guanacaste was the northeast (Cooley et al, 2019), coinciding with the distribution of M. modesta in this province (Amundrud et al, 2018; Hedstrom & Sahlen, 2001). The global distribution of M. modesta is limited by low annual precipitation and high annual mean temperature (Amundrud et al, 2018), suggesting that increased drought in Guanacaste will result in a contraction of its range toward the wetter areas of the province and expansion up mountain slopes.…”

The Water Availability on the Chinese Loess Plateau since the Implementation of the Grain for Green Project as Indicated by the Evaporative Stress Index

“…One explanation for why the SPEI and AI did not convey consistent information with the ESI is that the northern LP had higher magnitudes of increased temperature and relatively stable precipitation, which was beneficial for capturing drought information using the SPEI and AI [45]. Another possible reason was that the LAI of grass in the northern LP had a weak increase along with vegetation restoration, and the current climatic conditions may have enabled grass to continue to meet elevated evaporative demand with increased transpiration, consequently leading to a decreased ESI [46]. Some previous studies also reported that the ESI had reasonable spatial and temporal correlations with the SPI, SPEI and PDSI [44,47], while these three indices were calculated over a relatively long time scale and were, therefore, limited as indicators of short-term drought monitoring [48].…”